Pupillometry has been discovered to be an effective and useful non-invasive means of characterizing a subject's pupillary response and the condition of the human and animal autonomic nervous system. For example, in U.S. Pat. No. 5,187,506, Carter, it was disclosed therein that narcotics, opiates, depressants, stimulants, alcohol, and both legal and illegal drugs may produce deleterious and destructive effects on an individual's mental and physical performance. Pupillometry as described in the aforementioned patent is useful in detecting such drug or alcohol impairment. The teachings of U.S. Pat. No.5,187,506, Carter, are specifically incorporated herein by reference. Another useful and effective pupillometer is described in U.S. Pat. No. 4,755,043, Carter. This patent describes a portable, hand-held, dynamic, automatic scanning pupillometer which is operated by a user to view a subject's pupil, thereby obtain pupil images and to measure pupil size and dynamic reaction to a light stimulus. The teachings of U.S. Pat. No. 4,755,043 are also incorporated herein by reference.
A main difference between the Carter '506 patent and the Carter '043 patent is that the pupillometer of the Carter '506 patent is a desktop or other mechanically supported device which may be totally operated by an alert person whose pupil is to be imaged, while the Carter '043 patent teaches a pupillometer which is operated by a user and can be used to image the pupil of a subject in any posture and any state of alertness or consciousness. A distinct advantage of the pupillometer described in the Carter '506 patent is the incorporation of a self-centering means therein so that the user can easily and quickly center the image of the pupil on an image sensor to form an image thereof. The pupillometer of the '043 patent does not incorporate such a convenient aid to centering, and therefore an operator must painstakingly position the device to center the pupil to obtain an image thereof. The pupillometer of the Carter '506 patent employs a unique electronic centering means which allows the user to center the pupil on an optical semiconductive device in the optical block of the pupillometer by displaying an image of the pupil on a display device at the center of the user's field of view. This centering means has the disadvantage, however, that to the novice user, the pupil image is an unfamiliar, strange and poorly understood image and its movement relative to the user's gaze and head position can cause frustration and anxiety. This centering means also has the advantage of allowing an observer supervising the use of the instrument to coach the user during the centering process by referring to a duplicate of the pupil image displayed on the monitor of the host computer. This computer monitor image also allows the supervisor to judge from the shape and position of the pupil image whether a dropping eyelid or eyelashes are likely to degrade the measurement of pupil size and reactivity. Thus, on many occasions, the pupillometer of the Carter '506 patent while easy for the experienced user to operate, is simply inadequate to efficiently provide adequate pupil imaging and characterization for novice users such as subjects in clinical examinations.
Because of these aforementioned problems and deficiencies, the inventor of the subject matter herein claimed and disclosed has discovered that existing portable and tabletop pupillometers fail to solve needs in the art for compact, portable devices which provide efficient and easy to understand and use centering means under varied conditions of use. The aforementioned pupillometers do not provide the advantageous combination of compact size with centering aids to facilitate their use and therefore, do not fulfill a long-felt need in the art for a pupillometer to make rapid, accurate and reliable measurement of pupil size and reactivity while requiring minimum instruction and training of novice users.